1. Field of the Invention
The present invention relates to an apparatus for use in a hot isostatic pressing (hereinafter referred to simply as "HIP") treatment and, more particularly, to the same apparatus capable of shortening the cooling time after completion of HIP treatment thereby improving the operating efficiency.
2. Description of the Prior Art
Heretofore, an HIP apparatus has been basically composed of a high pressure vessel, a heat insulating layer and heater disposed inside the heat insulating layer, both the heat insulating layer and the heater being disposed within a high pressure chamber defined by upper and lower covers. In view of the importance of heat insulating and soaking performances, various improvements have been proposed in connection with an HIP apparatus as disclosed, for example, in Japanese Patent Publication Nos. 50276/80 and 53276/83.
On the other hand, since this HIP treatment involves the drawback that a long time is required for the execution of a single cycle, efforts have been demanded for rationalization of the entire process, and there has been developed what is called a modular type HIP system including a plurality of stations such as a cooling/preheating station and preparatory station.
However, one important factor in HIP treatment is cooling, and it is apparent that cooling has a great influence upon an efficient utilization of an HIP apparatus. For this reason, various improvements and the development of new systems have been made as mentioned above. Particularly as to HIP apparatus per se, improvements have been made with respect to the structure of the heat insulating layer and that of heater. But, there have been made few attempts to enhance the cooling effect, especially to enhance the cooling effect while circulating a high pressure gas.